02 July 2026
IMS became mandatory for all regular GSTR-3B filers from 1 April 2026; composition taxpayers are exempt. Inaction = deemed acceptance — an unreviewed invoice flows into your GSTR-2B as available ITC automatically. Section 38 of the CGST Act, substituted by Notification 16/2025-CT (17 Sep 2025), now ties ITC to accepted IMS records. The absolute locking of the ITC section in Form GSTR-3B from the July 2026 tax period is covered under GSTN Advisory No. 666. This enforces that Table 4 (ITC) is strictly auto-populated from GSTR-2B, which itself is completely formed based on your active choices (Accept/Reject/Pending) within the IMS.